Binary Black Hole Coalescence

A black hole is one of the most fascinating and enigmatic predictions of Einstein's theory of general relativity. Its interior can have rich structure and is intrinsically dynamical, where space and time itself are inexorably led to a singular state. The exterior of an isolated black hole is, on the other hand, remarkably simple, described uniquely by the stationary Kerr solution. The dynamics of black holes are governed by laws analogous to the laws of thermodynamics, and indeed when quantum processes are included, emit Hawking radiation with a characteristic thermal spectrum. Most remarkable however, is that black holes, “discovered” purely through thought and the mathematical exploration of a theory far removed from every day experience, appear to be ubiquitous objects in our universe.

The evidence that black holes exist, though circumstantial, is quite strong [1]. The high luminosity of quasars and other active galactic nuclei (AGN) can be explained by gravitational binding energy released through gas accretion onto supermassive (10⁶–10⁹M☉) black holes at the centers of the galaxies [2, 3], several dozen X-ray binary systems discovered to date have compact members too massive to be neutron stars and exhibit phenomena consistent with matter interactions originating in the strong gravity regime of an inner accretion disk [4], and the dynamical motion of stars and gas about the centers of nearby galaxies and our Milky Way Galaxy infer the presence of very massive, compact objects there, the most plausible explanation being supermassive black holes [5, 6, 7].